1. Field of the Invention
The present invention relates to a cell voltage detector for detecting the cell voltage of a fuel cell.
2. Description of the Related Art
A fuel cell that is installed in a fuel cell powered automobile is, as shown in FIG. 5, formed into a stack in which a number of cells 95 are stacked together which cells 95 are each formed by holding a solid polymer electrolyte membrane 91 such as a polymer ion exchange membrane with an anode 92 and a cathode 93 from both sides thereof and holding in turn the outsides of the anode 92 and the cathode 93 with a pair of separator 94, 94, and each cell 95 includes a fuel gas path 96 into which a fuel gas (for example, hydrogen gas) is supplied and an oxidant gas path 97 into which an oxidant gas (for example, air) is supplied.
In this fuel cell stack, hydrogen ions generated at the anodes 92 through catalytic reaction pass through the solid polymer electrolyte membranes 91 and travel to the cathodes 93, where hydrogen ions react with oxygen to cause electrochemical reaction to thereby generate electricity.
In the fuel cell stack constructed as described above, with a view to discovering cells that are not normal (namely, cells that fail or deteriorate) as early as possible, the electricity generating conditions of the respective cells 95 need to be controlled, and to this end, the voltage of each cell (hereinafter, referred to as cell voltage) is detected.
Then, in order to detect the cell voltage, pairs of separators 94, 94 of the respective cells 95 are connected, respectively, to voltage detection circuits 101 of an electronic control unit (ECU) 100.
Here, a connecting structure disclosed in JP-A-9-283166 is taken as a conventional connecting structure for connecting harnesses 102 connected to the voltage detection circuits 101 with the separators 94. In the connecting structure disclosed in this Japanese Unexamined Patent Publication, a mount hole is opened in each separator for mounting a terminal to the separator, and an output terminal provided at a distal end of each harness is inserted into this hole for connection.
In addition, according to another connecting structure, an output terminal is provided on the separator for measuring the voltage and a connector is provided at a distal end of each harness, so that the connector is connected to the output terminal of each separator.
In either of the conventional connecting structures, however, there is caused a problem that the connected components are easy to loosen or come off when they are subjected to vibrations. In particular, in an on-board fuel cell stack, there are many opportunities where the fuel cell stack is subjected to vibrations, and therefore, this problem cannot be ignored.
In addition, since the connecting portions are exposed, there is also caused a defect that water is liable to have access to the connecting portions so exposed.
Thus, the invention was made to provide a cell voltage detector for a fuel cell which can attempt to improve the ensured electrical connections between the separators of the fuel cell and the voltage detecting unit, as well as the waterproofness of the connecting portions where the separators and the voltage detecting unit are connected.
With a view to solving the problems, according to a first aspect of the invention, there is provided a cell voltage detector (for example, a cell voltage detector 1 in an embodiment which will be described with reference to FIGS. 1 and 2) for fuel cell (for example, a stack 40 in the embodiment which will be described with reference to FIG. 2) comprising terminals (for example, terminals 6 in the embodiment which will be described with reference to FIGS. 2 and 3) adapted to be brought into abutment with separators (for example, separators 41 in the embodiment which will be described with reference to FIG. 4) for the fuel cell and a voltage detecting unit (for example, a control unit 4 in the embodiment which will be described with reference to FIGS. 1, 2 and 3) for detecting the cell voltage of the fuel cell through the terminals, wherein the cell voltage detector further comprises a terminal holder (for example, a terminal holder 2 in the embodiment which will be described with reference to FIGS. 2 and 3) for holding one end of the respective terminals and permitting the abutment of the terminals with the separators via a terminal opening (for example, a terminal opening 34 in the embodiment which will be described with reference to FIGS. 2 and 3) opened in a fuel cell cover (for example, a fuel cell cover 30 in FIGS. 1 and 2) for encompassing the fuel cell, the terminal holder having a leg portion (for example, a leg portion 7 in the embodiment which will be described with reference to FIGS. 2 and 4) adapted to be brought into abutment with the periphery of the terminal opening and a terminal cover (for example, a terminal cover 3 in the embodiment which will be described with reference to FIGS. 1, 2 and 3) retained on the fuel cell Cover, so that the terminal cover is brought into abutment with a head portion (for example, a head portion 8 in the embodiment which will be described with reference to FIGS. 2 and 4) of the terminal holder on an inner surface thereof and covers the periphery of the terminal opening.
According to the construction, the terminal holder can be held with the fuel cell cover and the terminal cover there between in such a manner as to permit no movement thereof, and furthermore, the fuel cell cover, the terminal holder and the terminal cover can be made integral with each other. Additionally, the terminal holder and the terminal opening in the fuel cell cover can be covered with the terminal cover.
According to a second aspect of the invention, there is provided a cell voltage detector for fuel cell as set forth in the first aspect of the invention, wherein the fuel cell cover has a plurality of said terminal openings (for example, terminal openings 34, 34 in the embodiment which will be described with reference to FIGS. 2 and 3), wherein the terminal cover covers the plurality of terminal openings, and wherein the voltage detecting unit is disposed between the plurality of terminal openings which are covered with the terminal cover.
According to the construction, the space between the terminal openings can be utilized effectively.
According to a third aspect of the invention, there is provided a cell voltage detector for fuel cell as set forth in the first or second aspect of the invention, wherein the terminal holder has an elastic body (for example, a cushion 10 in the embodiment which will be described with reference to FIGS. 2 and 4) at least either at a distal end of the leg portion or at a distal end of the head portion.
According to the construction, vibrations can be absorbed by the elastic body.
According to a fourth aspect of the invention, there is provided a cell voltage detector for fuel cell as set forth in any of the first to third aspects of the invention, wherein the terminal holder has a pair of said leg portions (for example, leg portions 7, 7 in the embodiment which will be described with reference to FIGS. 2 and 4) disposed in such a manner as to straddle the terminal opening, and wherein the terminal holder holds the one end of the terminals between the pair of leg portions.
According to the construction, even when a load is applied from the terminal cover to the terminal holder, the terminal holder is made difficult to be displaced, and as a result, the terminals are made difficult to be displaced.